This invention relates to an electrochromic display (referred to as "ECD" hereinafter) which varies, reversibly, the degree of coloration or the transmission factor in response to a redox reaction occurring at or near the surfaces of electrodes in response to a voltage applied for displaying purposes, and more particularly, applied to a background plate for an ECD. An ECD utilizes the phenomenon which varies the light absorbency of an electrochromic material sandwiched between electrodes, that is, the so-called electrochromism. Well known electrochromic materials are viologen, WO.sub.3, MoO.sub.3, TiO.sub.2, Agl, polytungsten anion, etc. Nowadays research activities have been mostly directed to a family of the solution type using viologen and a family of the solid state type using tungsten oxide (WO.sub.3). The solution type of the ECD induces the coloring phonemenon by educing colored material on the surfaces of the electrodes from a solution, whereas the solid state type produces color centers having absorption within a visible light range in the solid state electrochromic material due to an electrochemical reaction.
One major feature of the ECD rests in that the ECD is of the passive type like liquid crystal displays and provide a high contrast and vivid display. In addition, enabling voltage is relatively small and less power is consumed because of the passive nature. It is further possible that a visual display may last for a long period of time with no sustain voltage applied because of the non-volatile memory properties inherent to the ECD. Other advantages of the ECD are that a wide display panel may be reduced to practice and so on. The ECD is applicable widely to segmented displays for use in digital timepieces, calculators, registers, etc., character, symbol or chart display panels with an X-Y matrix electrode assembly, light valves (projection type displays), light shutters, transmission light quantity regulators, etc. In view of the foregoing, the ECD represents a new promising display which provides a much more vivid display than liquid crystal displays, bears excellent appearance of a display background without polarizers, shows that the display performances are insensitive to changes in the viewing angle, consumes less power than light emitting diodes and avoids a degraded condition of display even within bright light surroundings. With a wider range of applications, it is desirable to provide the ECD with diversification of display patterns.
It is therefore an object of the present invention to provide a new and useful ECD which is fully compatible with varied display patterns without impairing the above listed advantages of the ECD.
Other objects and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description which is to be considered in conjunction with the accompanying drawings.